In Non Patent Literature 1, plate-like sodium niobate (general formula: NaNbO3, hereinafter, referred to as NN) grains formed by topochemical micro-crystal conversion (hereinafter, referred to as TMC) is used to control the crystallographic orientation of a piezoelectric ceramic including potassium sodium niobate as a main component. Non Patent Literature 1 reports that the piezoelectricity of the piezoelectric ceramic with a preferred crystal orientation is greatly improved compared with that of a non-oriented ceramic.
Non Patent Literature 2 reports that a solid solution of NN and barium titanate, {(1−x)NaNbO3-xBaTiO3, 0<x<0.2}, is a promising lead-free piezoelectric material having a high Curie temperature. The solid solution of NN and barium titanate is hereinafter referred to as NN—BT.
Non Patent Literature 3 reports that, through casting in a high magnetic field, the orientation of a piezoelectric ceramic can be controlled.